Trucks comprising a separable tractor and trailer typically utilize a substantially round coupling plate in combination with a mating pin. The coupling plate is mounted on the rear portion of the tractor and has a rearwardly open slot adapted to receive and lock the mating pin which is mounted under the forward portion of the trailer. These components are fairly standardized so that effectively any tractor can be coupled to any trailer. This type of hitch device is known in the trade as a "fifth wheel". One known example of a "fifth wheel" device is supplied by Holland Hitch Company of Holland, Mich.
In the coupling operation, the tractor backs to the trailer so that the open slot of the coupling plate engages the pin beneath the trailer and a coupling plate latch automatically snaps closed to lock the pin into engagement. When it is necessary to disengage the trailer from the tractor, a release handle associated with the coupling plate must be pulled to open the latch and enable the trailer and pin to be disengaged. The release handle is permanently attached to the coupling plate which is positioned beneath the trailer and the pin resides midway of the width of the trailer when engaged. A trailer is typically between 96 inches and 102 inches wide outside dimensions and the floor of the trailer resides between 40 inches and 46 inches in height above the ground. This results in a truck driver, in the process of releasing the latch and uncoupling the tractor from the trailer, having to reach beneath a trailer at about 43 inches above the ground inward by a distance as much as 34 inches from the trailer side (recognizing that the release handle extends outwardly about 17 inches from the center of the trailer). In addition, this coupling plate and release handle are located inboard of the tractor's rear wheels, which somewhat obstruct the driver's entry under the trailer during this operation.
When the loaded trailer is coupled to the tractor by means of the fifth wheel hitch device and the trailer's supporting leg is retracted, the weight of the forward end of the trailer rests on the fifth wheel. The amount of the total trailer weight transmitted to the fifth wheel is related not only to the total cargo weight, but also to the distribution of that weight along the length of the trailer. If the trailer weight bearing on the fifth wheel is great, and too much of that weight is carried by the tractor's front wheels, the tractor will be excessively difficult to steer. Conversely, if the weight carried by the front wheels of the tractor is too little and the weight on the tractor's rear wheels is comparatively high, the front end "floats", causing a loss of steering control. Thus, tractors in which the fifth wheel is fixedly positioned on the tractor frame may be difficult to steer under certain Toad conditions. It is for this reason that many truck tractors have fifth wheel apparatus which is mounted on a longitudinal track which permits the operator to position the fifth wheel rearward or forward to accommodate the weight distribution. Fifth wheel adjustability may be over a distance of up to three feet.
When a truck driver is of average height, reaching in that distance to pull the release handle is difficult because it may be farther than the length of his or her arm. When a truck driver is taller, the low height of the trailer is an obstacle to reaching under the trailer. In either instance, the truck driver is likely to dirty his or her clothing in the process of reaching under the trailer. Furthermore, due to exposure to the elements and other factors, the latch and release handle are frequently rusty, dirty and hard to pull, especially in such an awkward position. This combination of conditions does, at least occasionally, result in back or shoulder strain injury, and often dirty clothes.
A related device useful in uncoupling operations for certain tractor-trailer units is disclosed in U.S. Pat. No. 4,251,089 to Skaggs for a Tractor-Trailer Vehicle Decoupling Tool. The device of the Skaggs patent comprises a second class lever, having its point of force application positioned between its handle and its fulcrum. The Skaggs device is useful and is taught with the fulcrum being pressed against the rear wheels of the tractor and the handle extended upwardly. In certain situations, such as, for example a tractor having an adjustably positionable fifth wheel that is adjusted so the release handle of the fifth wheel is not aligned with a tractor rear wheel, the fulcrum of the Skaggs device would have no secure surface against which to bear. Nor could the Skaggs device be used effectively by placing its fulcrum against the side of the trailer and its handle downward, since that orientation would require the operator to crouch in a posture precluding a reasonable application of force, and possibly causing a back injury.
A related problem in the use of tractor-trailer trucks involves the rear wheel carriage. On many contemporary trailers, this rear carriage is positionally adjustable in the forward and rearward direction so as to improve the distribution of the load with respect to the wheels. In order to keep the proportion of the trailer load bearing on the coupling plate in reasonable limits, the rear wheel carnage may be moved forward when the load weight is predominantly toward the trailer nose and moved rearward when the load is toward the tail of the trailer.
Movement of the rear carriage and wheels is accomplished by the rear carriage being slidably mounted on a pair of rails beneath the trailer body. A latching mechanism is provided to engage a series of positioning holes in the rails. The latching mechanism is disengaged by pulling a latch handle so as to release latching pins connected to the latching mechanism. This latch handle is similarly located beneath the trailer body (as in the case of the coupling release handle described above) and one must reach under the trailer in a position which is somewhat awkward. In addition, while the person is holding the latch handle to release the latching mechanism, the trailer must be moved to effect the adjustment of position, thus involving a hazard of injury to the person holding the handle.
In addition to all of the above considerations, trucks typically have small compartments for the storage of tools. Therefore, any apparatus or tool developed for the above mentioned operations must be able to be stored in a small compartment.
It is therefore an objective of this invention to provide an apparatus to assist the truck driver in pulling the release handle to enable the uncoupling of a tractor from a trailer.
It is another objective of this invention to permit the truck operator to pull the hitch release handle and uncouple a trailer from a tractor while standing in an upright posture and thus enable the use of adequate force while minimizing the likelihood of injury.
It is an additional objective of this invention to provide a tractor-trailer uncoupling device which is effective regardless of the position of the fifth wheel with respect to the rear wheels of the tractor.
it is a still further objective of this invention to provide an apparatus to assist the truck driver in pulling a latch handle to allow adjustment of the position of the rear carriage and wheels of the trailer.
It is an additional objective of this invention to provide an apparatus to perform the needed functions which is within the storage size limitations of the tool compartment of a tractor.
Other objects and advantages will be more fully apparent from the following disclosure and appended claims.